Ski boots are known comprising an outer shell of plastic material, a sole, a leg portion pivotally mounted on the shell at bosses provided at the malleoli, and a plurality of clamping levers for the shell and leg portion to immobilize the skier's let and foot inside the boot.
During descent, ski mountaineering requires the leg portion to be rigidly clamped to the shell, whereas during ascent or walking, the leg portion has to be able to swivel longitudinally about the shell.
For this reason, devices have been proposed consisting of a lever disposed vertically on the rear of the leg portion and provided with a traction element which acts simultaneously as a device for closing the leg portion and for clamping the leg portion, or shank, to the shell.
U.S. Pat. No. 6,247,252, granted Jun. 19, 2001, to David Parisotto, discloses a telemark ski boot including a shell of plastic material and an inner sole. The shell is provided with a pair of parallel walls, and a flexible portion extends transversely to the shell in the metatarsus area. Leg piece 4 is joined to the shell by hinge 13. A control device, indicated generally by reference numeral 14, and including blade 15 and control lever 16 adjusts the inclination of the leg piece, or shank, with respect to the shell. The control device is located at the rear 20 of the ski boot, above the heel.
U.S. Pat. No. 6,708,425, granted Mar. 23, 2004, to David Parisotto, discloses a ski boot, particularly a ski-mountaineering or telemark boot. The boot comprises a shell made of plastic, a shank or leg piece hinged to the shell at the ankle, and a control mechanism 14 located at the rear portion of the boot for controlling the tilt of the shank relative to the boot. Lever 20 is hinged to a rear projection 24, and is movable between a work position which prevents rearward motion of the shank, and a release position. A ring 25, hinged to the lever, engages a recess 28 formed in the rear projection of the shell to prevent forward rotation of the shank with respect to the shell.
However, rear mounted, lever operated devices present certain drawbacks, in particular:                difficult to operate due to its position;        substantial bulk, requiring the construction of very tall leg portions which are difficult to adapt to small sizes or to women's boots, given the shape of their calves; and        susceptibility to damage by accidental impact with steps or rocks, thereby losing its operability.        